EP0546895B1 - Reduced vulnerability device to control a helicopter rotor through a swashplate - Google Patents

Description

The present invention relates to a device with reduced vulnerability for controlling a helicopter rotor by swashplates. More specifically, the present invention relates to a device for controlling the swashplate of a helicopter by hydraulic servos allowing the locking or breaking of a servo without compromising the safety of the device. This particular arrangement of the main rotor operating servos and associated controls is thus intended to allow the piloting of the apparatus to continue, in the event that one of them is seriously affected by a projectile.

Military helicopters are particularly exposed in enemy zones and can be damaged or neutralized by the destruction of one of the swashplate controls. Because of this risk, military requirements require that the swashplate control can continue normally, in the event that one of the controls is damaged.

Many devices have been proposed and all are based on the principle of redundancy of control units, which allows the emergency control system to intervene and operate in place of the faulty control unit. .

French patent FR-2 438 586 relates to this type of redundant control devices for oscillating plates of helicopter rotor. The swashplate control device in this patent includes at least four actuation units and five in the assembly shown in the Figures. Each actuation unit consists of an electric generator and a hydraulic pump associated with a controlled hydraulic cylinder, to form an autonomous unit. Only three actuation units are used at any given time, the others being considered as passive backup units, which can become active only in the event of failure of any of the first three, mainly due to a ballistic impact. This patent thus implements the well-known principle of a system for controlling the swashplate by at least four servos, at least three of which are used in normal operation, and the other or the others used automatically as back-up, in the event of failure of any of the first three. The device illustrated in this document uses for each actuation unit an electric generator which cooperates with a hydraulic cylinder and a hydraulic pump. This assembly is relatively complex and bulky, whether for each of the servo-controls, for their anchoring or for the disengagement operation. In addition, each actuation unit must have an electric generator with its own circuit.

The object of the present invention is to remedy the various drawbacks described above, and to provide a device with reduced vulnerability for controlling a helicopter rotor by swashplates, which has a backup system which intervenes automatically in the event of '' anomaly on an actuation unit, so as not to call for detection and intervention by the pilot, who is only warned of what is being done, this device being as picked up as possible in order to be robust and reliable.

The device with reduced vulnerability, according to the invention, relates to the operation of a lift and propeller rotor of a helicopter, by means of a mechanism with swashplates mounted coaxially on the drive shaft of the rotor. This swashplate mechanism comprises a turntable and a non-turntable, the turntable is coupled by its peripheral part individually with a rod for controlling the pitch of each blade of the rotor, and the non-turntable is coupled at four points which are evenly distributed around its periphery, to four hydraulic actuation servos. Each hydraulic actuator has a power cylinder, an anchoring system and a servo valve, three of the servos being used in normal operation and the fourth being used as backup, in case of failure of the other three. Each power actuator is supplied by a hydraulic circuit, independent of the hydraulic circuits of the other actuators, and which comprises the servo valve operated by a mechanical input, connected to the cockpit by a wheelhouse; each of the power cylinders comprising a disengageable anchoring system. Three of the servo valves have a structure arranged so as to be active in normal operation and block the anchoring system of each corresponding cylinder, and a servo valve has a structure arranged so as to be passive in normal operation and to keep the clutch disengaged. anchoring system for the corresponding power cylinder. Each of the mechanical inputs of these four servo valves includes a system which, above a force threshold on one of the three normally active servo valves, neutralizes this servo valve and initiates the operation of the normally inactive servo valve, which becomes operational in backup operation.

Preferably in order to have particularly compact servos, each servo valve is integrated into the corresponding power cylinder, so as to constitute a monobloc assembly which is constituted by the body of the servo valve and by the body of the power cylinder.

• un ensemble de distribution à boucle d'asservissement entre la position du corps du vérin de puissance et la position de l'entrée mécanique correspondante ;
• un système de commutation de cette boucle d'asservissement, de manière à la mettre dans l'état opposé à celui du fonctionnement normal du dispositif de commande du plateau cyclique.

In each monobloc assembly, each servo valve can include:

• a control loop distribution assembly between the position of the power cylinder body and the position of the corresponding mechanical input;
• a switching system for this control loop, so as to put it in the opposite state to that of normal operation of the swashplate control device.

Advantageously, the control loop has the feedback of the position of the body of the power cylinder, which acts directly on the position of the mechanical input mounted on the monobloc assembly, by means of a control system. connected to the mechanical input. This assembly is arranged so that a modification of the position of the mechanical input relative to the monobloc assembly, following a maneuver by the pilot, causes the displacement of the body of the power jack, that is to say the displacement of the monobloc assembly, until the mechanical input finds its initial relative position relative to this monobloc assembly. The control loop is connected to the supply pressure of the corresponding independent hydraulic circuit, and the control system is connected to the tank of this independent circuit; this control system comprising a control drawer which is connected to the mechanical input.

According to a preferred arrangement of the invention, each power cylinder is of differential section, and it comprises a piston with a rod connected to the anchoring system, so as to have an upper chamber and a lower chamber on the side of the rod, which are connected to the corresponding servo loop; so that, during the operation of the power cylinder, the lower chamber is always connected to the hydraulic circuit under pressure.

• un tiroir de by-pass du vérin de puissance monté dans la boucle d'asservissement ;
• un piston de commutation à deux positions ;
• un distributeur de commutation agissant sur le piston de commutation pour avoir les deux positions :
  • . une position initiale dans laquelle le piston de commutation coopère avec le tiroir de by-pass, afin d'obtenir le fonctionnement normal du servodistributeur du vérin de puissance correspondant ;
  • . une position de secours dans laquelle le piston de commutation coopère avec le tiroir de by-pass, afin d'obtenir le fonctionnement de sauvegarde du servodistributeur du vérin de puissance correspondant.

Preferably, the switching system of the control loop comprises:

• a power cylinder bypass drawer mounted in the servo loop;
• a two-position switching piston;
• a switching distributor acting on the switching piston to have the two positions:
  • . an initial position in which the switching piston cooperates with the bypass slide, in order to obtain normal operation of the servo valve of the corresponding power cylinder;
  • . an emergency position in which the switching piston cooperates with the bypass slide, in order to obtain the backup operation of the servo valve of the corresponding power cylinder.

• une position correspondant à la boucle d'asservissement sans pression,
• une position de fonctionnement du servodistributeur correspondant à la boucle d'asservissement sous pression.

Advantageously, the bypass drawer is mounted on the feed channel of the control loop, and it is connected to the tank so that this bypass drawer has at least two positions:

• a position corresponding to the pressureless control loop,
• an operating position of the servo valve corresponding to the pressure control loop.

In addition, the switching piston is locked in the emergency position by an additional lock.

In order to properly adapt to the structure of the servo-control described above, the mechanical input is advantageously provided with a lock which is carried by the bypass drawer. In addition, the pilot drawer and the switching distributor belong to the same part, which is the pilot lever connected to the mechanical input constituted by an input lever. This entry lever is preferably mounted under the body of the servo valve via a joint which is arranged at one of its ends, the other end receiving the entry movement via the corresponding system. , and the pilot lever being connected to the input lever by a joint arranged between the movement input and the articulation of the mounting of this input lever. The input lever cooperates with two stops, a high stop and a low stop which are integral with the body of the servo valve. Finally, the input lever may include a housing which is arranged on the upper side of the mounting articulation, this housing receiving the lock carried by the bypass drawer which comes to block the input lever. More specifically, this housing and this lock have a conjugate profile of substantially frustoconical shape. The mounting lever mounting articulation is supported by two ears which are arranged under the body of the servo valve.

In order to be able to allow the device of the invention to operate correctly, the control lever may comprise, at the end opposite to the input lever, an elastic return system. This elastic return system is constituted, in a first embodiment, by a compression spring mounted between the body of the servo valve and the end of the pilot lever. In a second embodiment, the elastic return system consists of a compression spring mounted on a rod of the pilot lever between two washers disposed at each of its ends and held by a flange, a washer being applied to a support of the servo valve body, and a washer applying to another support of this body.

Finally, the pilot lever can include a shock absorber which becomes effective after a certain stroke thereof, so as to prevent it from going to its extreme positions in the event of rapid maneuvering.

• un tiroir de pilotage monté sur le levier de pilotage et entouré d'une chambre annulaire avec une chambre inférieure et une chambre supérieure situées de part et d'autre du tiroir de pilotage ;
• un tiroir de by-pass avec une tige sur laquelle est monté un ressort qui s'appuie d'une part sur ce tiroir et d'autre part sur le piston de commutation, et qui est disposé dans une chambre, l'autre extrémité du tiroir de by-pass ayant un chanfrein, et venant en contact avec le corps sous l'action du ressort, une chambre annulaire étant disposée autour de ce tiroir qui possède un canal débouchant dans la chambre ;
• la boucle d'asservissement ayant un canal qui relie la chambre supérieure du vérin de puissance à la chambre annulaire, reliée elle-même par un autre canal à la chambre annulaire du pilotage, et un canal reliant la chambre inférieure du vérin de puissance au tiroir de by-pass qui est relié par un autre canal à la chambre inférieure du pilotage ;
• un canal est relié à l'alimentation du circuit hydraulique et à un autre canal qui aboutit au tiroir de by-pass ;
• un canal est relié au retour du réservoir aboutissant dans la chambre supérieure du pilotage qui est reliée par un canal à la chambre du tiroir de by-pass ;
  de manière que, lorsque le circuit hydraulique est sous pression, le tiroir de by-pass se déplace sous l'action de la pression du canal de liaison pour mettre en communication la chambre inférieure du vérin de puissance avec la chambre inférieure du pilotage par l'intermédiaire des canaux correspondants, qui sont reliés alors aux canaux d'alimentation sous pression, et que, sous l'action d'un déplacement du levier de pilotage, le tiroir de pilotage se déplace pour mettre en communication la chambre supérieure du vérin avec la chambre inférieure de ce vérin ou avec la chambre supérieure du pilotage suivant le sens du déplacement du levier, afin que le corps du vérin se déplace jusqu'au retour à la position d'équilibre du tiroir de pilotage.

According to a preferred embodiment of the invention, each of the three servo valves active in normal operation comprises:

• a pilot drawer mounted on the pilot lever and surrounded by an annular chamber with a lower chamber and an upper chamber located on either side of the pilot drawer;
• a bypass drawer with a rod on which is mounted a spring which rests on the one hand on this drawer and on the other hand on the switching piston, and which is arranged in a chamber, the other end of the bypass drawer having a chamfer, and coming in contact with the body under the action of the spring, an annular chamber being arranged around this drawer which has a channel opening into the chamber;
• the control loop having a channel which connects the upper chamber of the power cylinder to the annular chamber, itself connected by another channel to the annular piloting chamber, and a channel connecting the lower chamber of the power cylinder to the drawer by-pass which is connected by another channel to the lower piloting chamber;
• a channel is connected to the power supply to the hydraulic circuit and to another channel which leads to the bypass drawer;
• a channel is connected to the return of the tank terminating in the upper piloting chamber which is connected by a channel to the chamber of the bypass drawer;
  so that, when the hydraulic circuit is under pressure, the by-pass slide moves under the action of the pressure of the connecting channel to put the lower chamber of the power cylinder into communication with the lower chamber of piloting by l intermediary of the corresponding channels, which are then connected to the pressurized supply channels, and that, under the action of a displacement of the pilot lever, the pilot valve moves to put the upper chamber of the jack in communication with the lower chamber of this actuator or with the upper pilot chamber in the direction of movement of the lever, so that the body of the actuator moves until returning to the equilibrium position of the pilot drawer.

• un tiroir de commutation qui est monté sur le levier de pilotage avec une chambre inférieure et une chambre supérieure situées de part et d'autre du tiroir de commutation ;
• un piston de commutation monté dans le corps et dans le prolongement du tiroir de by-pass, de manière que le ressort de ce tiroir s'appuie sur ce piston ;
• un système de canaux reliant le fond du piston de commutation à la chambre inférieure et à la chambre supérieure ainsi qu'à l'alimentation ;
  de manière que, lorsque le levier de pilotage se déplace vers le haut ou vers le bas d'une valeur supérieure à la valeur admise, il mette en communication l'une des chambres de pilotage avec l'alimentation, celle-ci étant alors envoyée par le canal correspondant sur le piston de commutation, qui se déplace pour se mettre en position de secours et repousse le tiroir de by-pass qui met alors en communication les chambres du vérin de puissance avec le retour au réservoir, par le système de canaux correspondants.

Each of the three active servo distributors normal operation may also include:

• a switch drawer which is mounted on the pilot lever with a lower chamber and an upper chamber located on either side of the switch drawer;
• a switching piston mounted in the body and in the extension of the bypass drawer, so that the spring of this drawer is supported on this piston;
• a channel system connecting the bottom of the switching piston to the lower chamber and to the upper chamber as well as to the supply;
  so that when the pilot lever moves up or down by a value greater than the accepted value, it puts one of the pilot chambers in communication with the power supply, the latter being then sent by the corresponding channel on the switching piston, which moves to go to the emergency position and pushes the bypass drawer which then puts the chambers of the power cylinder into communication with the return to the tank, by the channel system correspondents.

In addition, a connection channel provided with a throttle can connect the return channel to the tank and the supply channel of the switching cylinder. In order to further improve the operation of the switching, the end of the switching piston may include a recess constituting an end chamber. An additional lock can be mounted perpendicular to the axis of the switching piston, and it is then pushed by a spring, so as to be able to come and engage in a groove provided in the switching piston.

Finally, each servo valve active in normal operation preferably comprises a damper drawer, which is mounted on the pilot lever with a flange separating a lower chamber from an upper chamber, which are both connected to the supply channel by a system of channels, the collar having at least one constriction which connects the two chambers.

• un tiroir de pilotage qui est monté sur le levier de pilotage et qui est entouré d'une chambre annulaire, avec une chambre inférieure et une chambre supérieure situées de part et d'autre du tiroir de pilotage ;
• un tiroir de by-pass avec une tige sur laquelle est monté un ressort qui s'appuie d'une part sur ce tiroir et d'autre part sur le corps, et qui est disposé dans une chambre, l'autre extrémité du tiroir de by-pass ayant un chanfrein, et venant en contact avec le corps sous l'action du ressort, une chambre annulaire étant disposée autour de ce tiroir qui possède un canal débouchant dans la chambre ;
• la boucle d'asservissement ayant :
  • . un canal qui relie la chambre supérieure du vérin à la chambre annulaire du tiroir de by-pass, reliée elle-même par un canal à la chambre annulaire de pilotage ;
  • . et un canal reliant la chambre inférieure du vérin au tiroir de by-pass, qui est relié par un canal à la chambre inférieure du pilotage ;
• des canaux reliés à l'alimentation du circuit hydraulique qui aboutissent au tiroir de by-pass, la chambre du tiroir de by-pass étant reliée par un système de canaux au retour au réservoir en passant par la chambre supérieure de pilotage ;
  de manière que lorsque le circuit hydraulique est sous pression, le tiroir de by-pass se déplace sous l'action de la pression du canal d'alimentation, tout en laissant les chambres supérieure et inférieure du vérin de puissance reliées au retour au réservoir, afin que le servodistributeur passif reste inopérant.

According to a preferred embodiment of the invention, the passive servo valve in normal operation comprises:

• a pilot drawer which is mounted on the pilot lever and which is surrounded by an annular chamber, with a lower chamber and an upper chamber situated on either side of the pilot drawer;
• a bypass drawer with a rod on which is mounted a spring which rests on the one hand on this drawer and on the other hand on the body, and which is arranged in a chamber, the other end of the drawer bypass having a chamfer, and coming into contact with the body under the action of the spring, an annular chamber being disposed around this drawer which has a channel opening into the chamber;
• the control loop having:
  • . a channel which connects the upper chamber of the jack to the annular chamber of the by-pass drawer, itself connected by a channel to the annular pilot chamber;
  • . and a channel connecting the lower chamber of the jack to the bypass drawer, which is connected by a channel to the lower pilot chamber;
• channels connected to the supply to the hydraulic circuit which lead to the bypass drawer, the chamber of the bypass drawer being connected by a system of channels to the return to the tank passing through the upper pilot chamber;
  so that when the hydraulic circuit is under pressure, the bypass slide moves under the action of the pressure of the supply channel, while leaving the upper and lower chambers of the power cylinder connected to the return to the tank, so that the passive servo valve remains inoperative.

• un tiroir de commutation qui est monté sur le levier de pilotage avec une chambre centrale et deux portées : une portée inférieure et une portée supérieure situées de part et d'autre de cette chambre centrale ;
• un piston de commutation monté dans le corps et dans le prolongement du tiroir de by-pass ;
• des canaux reliant le fond du piston de commutation à la chambre centrale du tiroir de commutation qui est relié lui-même par d'autres canaux à l'alimentation sous pression, qui agit sur le piston de commutation, pour le maintenir en position basse initiale, un système de canaux raccordé au retour au réservoir aboutissant aux portées inférieure et supérieure du tiroir de commutation ;
  de manière que, lorsque le levier de pilotage se déplace vers le haut ou vers le bas, d'une valeur supérieure à la valeur admise, il mette en communication la chambre centrale de commutation avec l'un des canaux reliés au retour au réservoir, le piston de commutation peut alors se déplacer sous l'action du tiroir de by-pass poussé par la pression pour se mettre en position de secours, ce tiroir de by-pass met de ce fait en communication la chambre inférieure du vérin de puissance avec la chambre inférieure du tiroir de pilotage par les canaux correspondants, qui sont ainsi reliés à l'alimentation, et le tiroir de by-pass supprime la liaison avec le retour au réservoir de la chambre supérieure du vérin de puissance, ce qui permet au servodistributeur passif de devenir opérationnel.

In addition, the passive servo valve in operation normal includes:

• a switching slide which is mounted on the pilot lever with a central chamber and two ranges: a lower range and an upper range located on either side of this central chamber;
• a switching piston mounted in the body and in the extension of the bypass drawer;
• channels connecting the bottom of the switching piston to the central chamber of the switching slide which is itself connected by other channels to the pressurized supply, which acts on the switching piston, to keep it in the initial low position , a system of channels connected to the return to the tank leading to the lower and upper ranges of the switching slide;
  so that, when the pilot lever moves up or down, by a value greater than the accepted value, it puts the central switching chamber into communication with one of the channels connected to the return to the tank, the switching piston can then move under the action of the bypass drawer pushed by pressure to go into the emergency position, this bypass drawer therefore places the lower chamber of the power cylinder in communication with the lower chamber of the control drawer by the corresponding channels, which are thus connected to the power supply, and the by-pass drawer eliminates the connection with the return to the tank of the upper chamber of the power cylinder, which allows the servo valve passive to become operational.

In order to improve the operation of this passive servo valve in normal operation, the end of the switching piston may include a recess constituting an end chamber. In addition, an additional lock can be mounted perpendicular to the axis of the switching piston, this additional lock then being pushed by a spring, so as to be able to come to engage in a groove fitted in the switching piston. Finally, the passive servo valve in normal operation may include a damping drawer, which is mounted on the pilot lever with a flange separating a lower chamber from an upper chamber, which are each connected to the supply by a system of channels, the collar having at least one constriction connecting the two chambers to one another.

Advantageously, each servo-control of the device according to the invention comprises an anchoring system which is constituted by an anchoring cylinder having means of connection with the power cylinder and whose hydraulic circuit is connected to the lower chamber of this power cylinder, the anchor cylinder being linked to an element of the structure of the helicopter by hooking means.

More specifically, this anchoring cylinder comprises a body with a rod carrying two pistons which slide in this body and which determine, with this rod and this body, a chamber.

Advantageously, according to the invention, the rod of the power cylinder and the rod of the anchoring cylinder are one and the same part which constitute the means of connection of the anchoring cylinder with the power cylinder. On the other hand, the hydraulic circuit supplying the anchoring cylinder is constituted by a channel, which is arranged in the rods of the power cylinder and of the anchoring cylinder, so as to directly connect the chamber of the cylinder. anchoring to the lower chamber of the power cylinder. In addition, the two pistons of the anchoring cylinder are held on the rod on the one hand by a collar, and on the other hand by another end collar, which both belong to this rod, a spring pushing the two pistons relative to each other to hold them in place, one of the pistons pressing against a support of the body of the anchoring cylinder and the other piston applying against the edge of this body.

In the preferred embodiment of the invention, the hooking means of the anchoring cylinder comprise a hinge which is connected on the one hand to an element of the structure of the helicopter, and on the other hand to the bottom of the body of this anchor cylinder.

The present invention thus relates to a device with reduced vulnerability for controlling a helicopter rotor by swashplates, the non-rotating plate of which is coupled to four hydraulic actuating servo-controls. Each hydraulic servo drive has a power cylinder connected to an anchoring system and controlled by a servo valve. In this device, according to the invention, 'three hydraulic actuating servos are active in normal operation, while the fourth servo is in standby. Each hydraulic actuating servo-control is powered by an independent hydraulic generation, and the servo-distributor forms with the corresponding power cylinder a monobloc assembly which has a disengageable anchoring; the three active servos having their anchoring blocked, while the fourth emergency servo has its anchoring which is disengaged.

The architecture specific to the invention makes it possible, in preferred modes, to have monobloc or single-body servos, which are therefore less bulky, less expensive and less heavy than servos with separate bodies. In addition, since the hydraulic circuits are each assigned to a servo-control, a breakdown or damage to one or the other of these circuits has no effect on the other servo-control-hydraulic circuit arrangements. These servo controls also have the advantage of being directly connected to hydraulic anchoring devices, unlike electrical anchoring systems, which require specific detections and commands to synchronize the engagement and disengagement of anchors and servos.

The invention can also make it possible to have automatic detections and conversions, without any intervention from the pilot who is only informed of what is being done. In addition, the detection of the blocking or of the start in abutment of a servo control can be done by force detection on the input lever. This is possible due to the fact that there are three active servo drives, because the effort appears only on the one in question. With four active servos, the force also appears on the servo opposite it, and therefore the use of four active servos is not applicable to the system of the invention.

• la Figure 1 est une vue schématique en perspective de l'ensemble du dispositif à vulnérabilité réduite pour la commande d'un rotor d'hélicoptère par plateaux cycliques, selon l'invention, avec quatre unités d'actionnement ;
• la Figure 2 est une vue en perspective de l'adaptation des timoneries classiques pour la commande en tangage et en roulis des quatre unités d'actionnement, selon l'invention ;
• la Figure 3 est une vue générale en coupe suivant l'axe des vérins et des tiroirs d'une servocommande active en fonctionnement normal, le circuit hydraulique étant sans pression ;
• la Figure 4 est une vue générale en coupe suivant l'axe des vérins et des tiroirs d'une servocommande passive en fonctionnement normal, ce circuit hydraulique étant sans pression ;
• la Figure 5 est une vue analogue à la Figure 3, le circuit hydraulique étant sous pression, ce qui correspond à la position embrayée en fonctionnement normal ;
• la Figure 6 est une Figure analogue à la Figure 3, le circuit hydraulique étant sous pression, et les différents éléments étant en phase de débrayage au moment de la panne ;
• la Figure 7 est une Figure analogue à la Figure 3, le circuit hydraulique étant sous pression, et les différents éléments étant en phase débrayée après la panne ;
• la Figure 8 est une vue analogue à la Figure 4, le circuit hydraulique étant sous pression, ce qui correspond à la position débrayée en fonctionnement normal ;
• la Figure 9 est une Figure analogue à la Figure 4, le circuit hydraulique étant sous pression, et les différents éléments étant en phase d'embrayage au moment de la panne ;
• la Figure 10 est une Figure analogue à la Figure 4, le circuit hydraulique étant sous pression, et les différents éléments étant embrayés après la panne.

Other advantages will emerge from the invention which will be better understood with the aid of the description given below of particular embodiments, described without limitation, with reference to the appended drawings in which:

• Figure 1 is a schematic perspective view of the assembly of the reduced vulnerability device for controlling a helicopter rotor by swashplates, according to the invention, with four actuation units;
• Figure 2 is a perspective view of the adaptation of conventional wheelhouses for pitch and roll control of the four actuation units, according to the invention;
• Figure 3 is a general sectional view along the axis of the cylinders and drawers of a servo drive active in normal operation, the hydraulic circuit being without pressure;
• Figure 4 is a general sectional view along the axis of the cylinders and drawers of a passive servo drive in normal operation, this hydraulic circuit being without pressure;
• Figure 5 is a view similar to Figure 3, the hydraulic circuit being under pressure, which corresponds to the engaged position in normal operation;
• Figure 6 is a Figure similar to Figure 3, the hydraulic circuit being pressurized, and the various elements being in the declutching phase at the time of the failure;
• Figure 7 is a Figure similar to Figure 3, the hydraulic circuit being under pressure, and the various elements being in the disengaged phase after the failure;
• Figure 8 is a view similar to Figure 4, the hydraulic circuit being under pressure, which corresponds to the disengaged position in normal operation;
• Figure 9 is a Figure similar to Figure 4, the hydraulic circuit being pressurized, and the various elements being in the clutch phase at the time of failure;
• Figure 10 is a Figure similar to Figure 4, the hydraulic circuit being pressurized, and the various elements being engaged after the failure.

The reduced vulnerability device for controlling a helicopter rotor by swashplates is shown schematically in perspective in Figure 1. The reduced vulnerability device for the operation of a helicopter lift and propeller rotor is done by l 'Intermediate of a swash plate mechanism, which are mounted coaxially on the rotor drive shaft 6. The swash plate mechanism comprises a turntable and a non-turntable; the turntable is coupled by its peripheral part individually with a rod for controlling the pitch of each blade of the rotor, and the non-turntable 5 is coupled at four points 1, 2, 3, 4, which are evenly distributed at its periphery, with four hydraulic actuation servos. Each hydraulic actuation servo includes a power cylinder 9, an anchoring system 10 and a servo valve 41, 42. These hydraulic actuation servos are arranged at the periphery of the main gearbox 7 of the helicopter and each anchoring system 10 is mounted on an element 11 of the structure of the helicopter.

According to the invention, three of the servos are used in normal operation, and the fourth is used as backup in the event of failure of one of the other three, so that the control is always ensured by three servos.

The wheelhouse, referenced 13 as a whole, of control is arranged so as to ensure the movements of the three normally active servos, as well as the movements of the fourth normally passive servos, to control the tilting of the swashplate controlling the rotor in pitch and in roll. The wheelhouse 13 has a cyclic handle 12, which is arranged in the cockpit and which is mounted on a joint 16, so as to be able to pivot from left to right for controlling the roll movements, and from front to rear for control of pitch movements. These various movements are made thanks to the articulation 16 around an axis 15 of longitudinal pivoting for the movements from left to right of roll, and around an axis 17 of transverse pivoting for the movements of forward and backward pitching . The articulation 16 is disposed at the lower part of the cyclic handle 12, which extends below this articulation 16 by a lever 14. A connecting shaft 18 is mounted along the transverse pivot axis and ends in a fork which receives the cyclic handle 12 with its articulation 16. A connecting rod 19 has one of its ends which is mounted by an articulation 31 at the lower fork-shaped end of the lever 14. The connecting shaft 18 comprises at its other end a lever 25 which is provided with a hinge 36, in order to receive the end of a connecting rod 20. This connecting rod connection 20 is itself connected at its other end by a hinge 37 to a lifting beam 28, which rotates around a pivot axis 30 by a hinge 38. This lifting beam 28 is provided at each of its ends, on the one hand an articulation 39 on which the end of the linkage 21 is mounted for the control of point 1, and on the other hand at its other end an articulation 40 for the control of the linkage 23 of point 3. The connecting rod 19, which is mounted on the end of the lever 14 by the joint 31, has its other end which is mounted by means of a joint 32 on the fork of a lever 26, which rotates around a pivot pin 29 on which a lifter 27 is mounted by means of a hinge 33. This lifter 27 has at each of its ends, on the one hand, a hinge 34 on which is mounted the end of the linkage 22 for the command of point 2, and on the other hand to so at the other end, it is provided with a hinge 35 on which the end of the linkage 24 for controlling point 4 is mounted.

The control movements of the cyclic handle 12 from left to right for the roll cause opposite movements of the articulation 31 of the lever 14, which moves along its axis the connecting rod 19, thus causing it to rotate relative to the pivot axis 29 the end of the lever 26 and therefore the rotation of the lifter 27, that is to say the displacement along their axes of the control rods 22 and 24 of the points 2 and 4. The control movements from front to back of the cyclic handle 12 for the pitching movements rotate around its axis the connecting shaft 18, which rotates the lever 25 and moves along its axis the connecting rod 20, which at its turn controls in rotation around the pivot axis 30 the lifter 28, which drives along their axes the linkages 21 and 22 for controlling points 1 and 3.

• un vérin de puissance 9,
• un système d'ancrage 10 dudit vérin de puissance 9,
• un servodistributeur, référencé 41 ou 42 suivant le cas, qui est alimenté en fluide hydraulique sous pression et dans lequel s'introduit la commande mécanique d'entrée.

In the following description, the term servo-control means all of each of the four mechanisms coupled to the non-rotating swashplate 5. Each of these servo-controls comprises:

• a power cylinder 9,
• an anchoring system 10 of said power cylinder 9,
• a servo valve, referenced 41 or 42 as the case may be, which is supplied with pressurized hydraulic fluid and into which the mechanical input control is introduced.

Each of the linkages 21, 22, 23 and 24 are respectively connected to the mechanical input control of the corresponding servo-control at points 1, 2, 3 and 4 of the non-rotating plate 5.

The collective pitch control which, by suitable linkages, transmits the movements of the collective pitch lever simultaneously and for the same values to the mechanical inputs of the four servo controls, has not been shown, since it is carried out in a conventional and well known manner.

• quatre générations hydrauliques alimentant chacune une servocommande,
• les servocommandes sont à simple corps avec un ancrage débrayable,
• trois servocommandes sont actives avec leurs ancrages bloqués,
• une quatrième servocommande est passive, c'est-à-dire qu'elle est en by-pass avec son ancrage maintenu par un seuil,
• l'entrée mécanique des servocommandes actives comporte un système qui, au-dessus d'un seuil d'effort, déclenche :
  • . la mise en by-pass du vérin de puissance 9,
  • . le débrayage de l'ancrage 10,
• l'entrée mécanique de la servocommande passive comporte un système qui, au-dessus d'un seuil d'effort, déclenche :
  • . la mise en fonctionnement de la servocommande,
  • . le blocage de l'ancrage 10.

The device with reduced vulnerability for maneuvering a lift and propeller rotor of a helicopter essentially comprises:

• four hydraulic generations each supplying a servo drive,
• the servo drives are single-body with a detachable anchor,
• three servos are active with their anchors locked,
• a fourth servo drive is passive, that is to say it is in bypass with its anchoring maintained by a threshold,
• the mechanical input of active servo controls includes a system which, above a force threshold, triggers:
  • . the bypass of the power cylinder 9,
  • . disengaging the anchor 10,
• the mechanical input of the passive servo control includes a system which, above a force threshold, triggers:
  • . the activation of the servo control,
  • . blocking the anchor 10.

• chaque vérin de puissance 9 est alimenté par un circuit hydraulique, indépendant des circuits des autres vérins de puissance 9, ce circuit hydraulique comprenant le servodistributeur 41 ou 42 suivant le cas, qui est manoeuvré par une entrée mécanique et relié au poste de pilotage par la timonerie (13) et la timonerie de pas collectif non représentée ;
• chaque vérin de puissance 9 comporte un système d'ancrage débrayable ;
• les trois servodistributeurs 41 ont une structure agencée, de manière à être actifs en fonctionnement normal et à bloquer le système d'ancrage de chaque vérin de puissance 9 correspondant, et le servodistributeur 42 a une structure agencée, de manière à être passif en fonctionnement normal et à maintenir débrayé le système d'ancrage du vérin de puissance 9 correspondant ;
• chacune des entrées mécaniques de ces quatre servodistributeurs 41, 42 comporte un système qui, au-dessus d'un seuil d'effort sur l'un des trois servodistributeurs 41 normalement actifs, neutralise ce servodistributeur et initie la mise en fonctionnement du servodistributeur 42 normalement inactif, qui devient opérationnel en fonctionnement de sauvegarde.

Thus, according to the invention:

• each power cylinder 9 is supplied by a hydraulic circuit, independent of the circuits of the other power cylinders 9, this hydraulic circuit comprising the servo valve 41 or 42, as the case may be, which is operated by a mechanical input and connected to the cockpit by the wheelhouse (13) and the collective wheelhouse not shown;
• each power cylinder 9 comprises a disengageable anchoring system;
• the three servo valves 41 have a structure arranged so as to be active in normal operation and to block the anchoring system of each corresponding power cylinder 9, and the servo valve 42 has a structure arranged so as to be passive in normal operation and to keep the anchoring system of the corresponding power cylinder 9 disengaged;
• each of the mechanical inputs of these four servo valves 41, 42 comprises a system which, above a force threshold on one of the three normally active servo valves 41, neutralizes this servo valve and initiates the operation of the servo valve 42 normally inactive, which becomes operational in backup operation.

FIG. 3 represents the assembly of a normally active servo-control and FIG. 4 represents the normally passive servo-control, both of these servo-controls having their hydraulic circuits not supplied, that is to say without pressure, which correspond to the helicopter on the ground. Each servo normally active comprises a servo valve 41 which supplies a power cylinder 9 connected to an anchoring cylinder 10, the mechanical input being constituted by an input lever 49. The servo valve 41 is integrated into the power cylinder 9, so that the body 45 of the servo valve 41 and the body 47 of the power cylinder 9 constitute a single monobloc assembly 43 on which the input lever 49 is mounted. Likewise, the passive servo control consists of the servo valve 42, the power cylinder 9 and the corresponding anchoring cylinder 10, the mechanical input being constituted by an input lever 49. The servo valve 42 is integrated into the power cylinder 9, so that the body 46 of the servo valve 42 and the body 47 of the cylinder of power 9 constitute a single monobloc assembly 44 on which the input lever 49 is mounted. Thus, according to the embodiments shown in FIGS. 3 and 4, the power jacks 9, the anchoring cylinders 10 and the mechanical input systems with the input lever 49 are identical, while the servo valves 41 and 42 have a hydraulic circuit and elements which are specific to them.

• un ensemble de distribution à boucle d'asservissement entre la position du corps 47 du vérin de puissance 9 et la position de l'entrée mécanique correspondante ;
• un système de commutation de cette boucle d'asservissement, de manière à la mettre dans l'état opposé à celui du fonctionnement normal du dispositif de commande du plateau non tournant 5 des plateaux cycliques.

Each of the servo valves 41, 42 includes:

• a control loop distribution assembly between the position of the body 47 of the power cylinder 9 and the position of the corresponding mechanical input;
• a switching system for this control loop, so as to put it in the state opposite to that of normal operation of the device for controlling the non-rotating plate 5 of the cyclic plates.

The control loop establishes a link between the position of the body 47 of the power cylinder 9, that is to say the position of the corresponding monobloc assembly 43, 44, and the position of the mechanical input which is mounted on this monobloc assembly 43, 44 by a control system connected to the mechanical input. The control loop thus has the feedback of the position of the body 47 of the power cylinder 9, which acts directly on the position of the mechanical input mounted on the corresponding monobloc assembly 43, 44 by means of the control system connected to the mechanical input . Therefore, any modification of the position of the mechanical input relative to the monobloc assembly 43, 44, following a maneuver of the pilot, causes the displacement of the body 47 of the power cylinder 9, that is to say say that it causes the displacement of the corresponding monobloc assembly 43, 44, until the mechanical input finds its initial relative position relative to this monobloc assembly 43, 44.

To do this, the control loop is connected to the supply pressure of the corresponding independent hydraulic circuit, and the control system is connected to the tank of this independent circuit and it comprises a control drawer 82, 142 which is connected to the corresponding mechanical input.

Each power cylinder 9 is of differential section, and it comprises a piston 58 with a rod 59 connected to the anchoring system. Thus, the jack has an upper chamber 60 and a lower chamber 61 located on the side of the rod 59. The upper chamber 60 and the lower chamber 61 are both connected to the servo loop, so that , during the operation of the power cylinder 9, the lower chamber 61 is always connected to the hydraulic circuit under pressure.

Each anchoring system comprises an anchoring cylinder 10 which has connecting means with the corresponding power cylinder 9. Each anchoring cylinder 10 is linked to an element 11 of the structure of the helicopter by attachment means. In addition, according to a feature of the invention, the anchoring cylinder has its hydraulic circuit which is connected to the lower chamber 61 of the corresponding power cylinder 9.

The anchoring cylinder 10 comprises a body 63 and a rod 64 carrying two pistons referenced 65, which slide in the body 63 and which determine, with the rod 64 and the body 63, a chamber 72. The rod 64 of the cylinder anchoring 10 and the rod 59 of the corresponding power cylinder 9 form a single piece which constitutes the means of connection of this anchoring cylinder 10 with the power cylinder 9. The two pistons 65 are held on the rod 64 by a flange 67 located in the direction of the power cylinder 9, and by another end flange 68 which both belong to the rod 64. In addition, a spring 66 is mounted on this rod 64 between the two pistons 65, so as to push these two pistons relative to each other to hold them in place, so that a piston 65 is applied against a support 69 arranged in the bottom inside the body 63 , and that the other piston 65 is pressed against the edge 70 of this body 63 located on the side opposite, that is to say on the side of the power cylinder 9. Thus, the body 63 of the anchoring cylinder 10 has a support 69, which determines at the lower part of this anchoring cylinder 10 a clearance chamber 73 allowing the displacement of the rod 64 inside the body 63. The attachment means of this anchoring cylinder 10 are mounted below the bottom 71 of the body 63 and consist of a joint 74, which is connected to on the one hand to the element 11 of the structure of the helicopter, and on the other hand to the bottom 71 of the body 63.

The hydraulic circuit for supplying the anchoring cylinder 10 is constituted by a channel 76 which is arranged in the rod 59 of the power cylinder 9 and in the rod 64 of the anchoring cylinder 10, so as to directly connect the chamber 72 from the anchoring cylinder 10 to the lower chamber 61 of the power cylinder 9.

In order to seal the hydraulic circuit of the anchoring cylinder 10, each of the two pistons 65 has seals 75 arranged inside and outside of these pistons, that is to say in contact respectively with the rod 64, and with the body 63.

Each power cylinder 9 is closed at its upper part by a clip 48 which is connected to the corresponding point of the periphery of the non-rotating plate 5. In order to ensure the tightness of this power cylinder 9, seals 62 are arranged at the lower part of the body 47 to cooperate with the rod 59, in the piston 58 and in the fastener 48, to be applied in the internal walls of the body 47.

• un tiroir de by-pass 81, 141 du vérin de puissance 9 qui est monté dans cette boucle d'asservissement ;
• un piston de commutation 85, 145 qui a deux positions ;
• un distributeur de commutation 83, 143 agissant sur le piston de commutation 85, 145 pour avoir les deux positions :
  • . une position initiale dans laquelle le piston de commutation 85, 145 coopère avec le tiroir de by-pass 81, 141, afin d'obtenir le fonctionnement normal du servodistributeur du vérin de puissance 9 correspondant ;
  • . une position de secours dans laquelle le piston de commutation 85, 145 coopère avec le tiroir de by-pass 81, 141, afin d'obtenir le fonctionnement de sauvegarde du servodistributeur 41, 42 du vérin de puissance 9 correspondant.

The servo loop switching system for each of the servos includes:

• a bypass drawer 81, 141 of the power cylinder 9 which is mounted in this control loop;
• a switching piston 85, 145 which has two positions;
• a switching distributor 83, 143 acting on the switching piston 85, 145 to have the two positions:
  • . an initial position in which the switching piston 85, 145 cooperates with the bypass slide 81, 141, in order to obtain normal operation of the servo valve of the corresponding power cylinder 9;
  • . an emergency position in which the switching piston 85, 145 cooperates with the bypass slide 81, 141, in order to obtain the backup operation of the servo valve 41, 42 of the corresponding power cylinder 9.

• une position correspondant à la boucle d'asservissement sans pression,
• une position correspondant à la boucle d'asservissement sous pression.

The switching system cooperates with the control loop by means of the bypass slide 81, 141 which is mounted on the supply channel 117, 118; 177, 178 of the control loop and which is connected to a source of pressurized hydraulic fluid, so that this bypass slide 81, 141 has at least two positions:

• a position corresponding to the pressureless control loop,
• a position corresponding to the pressure control loop.

The switching piston 85, 145 is locked in the emergency position by an additional lock, respectively referenced 86, 146.

In the embodiments shown in Figures 3, 4, the mechanical input is provided with a latch 51 which is carried by the bypass drawer 81, 141, which can thus act on the mechanical input. In addition, the pilot valve 82, 142 and the corresponding switching distributor belong to the same part which is a pilot lever 50 connected to the mechanical input constituted by the input lever 49.

Each mechanical input is constituted by the input lever 49 which is mounted under the body 45, 46 of the corresponding servo valve 41, 42. This input lever 49 is mounted by means of a hinge 52, which is arranged at one of the ends of this lever 49. The other end of the lever 49 receives the input movement via the corresponding system, and the pilot lever 50 is connected to the input lever 49 by a hinge 53, which is disposed between the movement input and the joint 52 of the mounting of this input lever 49. The input lever 49 is placed between two stops: a high stop 56 and a low stop 57 which are integral and fixed below the body 45, 46 of the corresponding servo valve 41, 42. The articulation 52 ensuring the mounting of the input lever 49 is supported by two ears 54, which are arranged under the body 45, 46 of the corresponding servo valve 41, 42. In addition, the input lever e 49 includes a housing 55 which is arranged on the upper side of the mounting joint 52, in order to receive the lock 51 carried by the bypass drawer 81, 141 in order to block the input lever 49. This housing 55 and latch 51 have a conjugate profile of substantially frustoconical shape.

Finally, each of the servo valves 41, 42 includes a shock absorber which is mounted on the pilot lever 50. This shock absorber becomes effective only after a certain stroke of the pilot lever, and it is intended to prevent it from going to its extreme positions in the event of rapid, but brief, operation of the input lever. The pilot lever 50 further comprises an elastic return system which is arranged at the end of this pilot lever 50, on the side opposite to the input lever 49.

• un tiroir de pilotage 82 qui est monté sur le levier de pilotage 50, et qui est entouré d'une chambre annulaire 97 avec une chambre inférieure 98 et une chambre supérieure 99 situées de part et d'autre du tiroir de pilotage 82 ;
• un tiroir de by-pass 81 qui a une tige 90 sur laquelle est monté un ressort 88, qui s'appuie d'une part sur ce tiroir 81, et d'autre part sur le piston de commutation 85 et qui est disposé dans une chambre 93, l'autre extrémité 107 du tiroir de by-pass 81 ayant un chanfrein 92, et venant en contact avec le fond du logement dans le corps 45 sous l'action du ressort 88, une chambre annulaire 94 étant disposée autour de ce tiroir 81 qui possède un canal 91 débouchant dans la chambre 93 ;
• la boucle d'asservissement qui a un canal 111 reliant la chambre supérieure 60 du vérin 9 à la chambre annulaire 94, reliée elle-même par un canal 113 à la chambre annulaire 97 du pilotage, et un canal 112 reliant la chambre inférieure 61 du vérin 9 à la chambre annulaire 94 du tiroir de by-pass 81, qui est reliée par un canal 114 à la chambre inférieure 98 du pilotage ;
• un canal 118 qui est relié à l'alimentation du circuit hydraulique, et qui est relié à un canal 117 qui aboutit au tiroir de by-pass 81 ;
• un canal 116 qui est relié au retour au réservoir de fluide hydraulique et qui aboutit dans la chambre supérieure 99 du pilotage, qui est reliée elle-même par un canal 115 à la chambre 93 du tiroir de by-pass 81.

As can be seen in FIG. 3, each of the three active servo valves 41 in normal operation comprises:

• a pilot drawer 82 which is mounted on the pilot lever 50, and which is surrounded by an annular chamber 97 with a lower chamber 98 and an upper chamber 99 located on either side of the pilot drawer 82;
• a bypass drawer 81 which has a rod 90 on which is mounted a spring 88, which rests on the one hand on this drawer 81, and on the other hand on the switching piston 85 and which is arranged in a chamber 93, the other end 107 of the bypass drawer 81 having a chamfer 92, and coming into contact with the bottom of the housing in the body 45 under the action of the spring 88, an annular chamber 94 being disposed around this drawer 81 which has a channel 91 opening into the chamber 93;
• the control loop which has a channel 111 connecting the upper chamber 60 of the jack 9 to the annular chamber 94, itself connected by a channel 113 to the annular chamber 97 of the pilot, and a channel 112 connecting the lower chamber 61 of the cylinder 9 to the annular chamber 94 of the bypass drawer 81, which is connected by a channel 114 to the lower chamber 98 of the piloting;
• a channel 118 which is connected to the supply to the hydraulic circuit, and which is connected to a channel 117 which ends at bypass drawer 81;
• a channel 116 which is connected to the return to the hydraulic fluid reservoir and which terminates in the upper chamber 99 of the piloting, which is itself connected by a channel 115 to the chamber 93 of the bypass drawer 81.

• un tiroir de commutation 83 monté sur le levier de pilotage 50 avec une chambre inférieure 101 et une chambre supérieure 102 qui sont situées de part et d'autre du tiroir de commutation 83 ;
• un piston de commutation 85 monté dans le corps 45 et dans le prolongement du tiroir de by-pass 81, de manière que le ressort 88 de ce tiroir 81 s'appuie sur ce piston 85 ;
• un canal 122 qui relie le fond du piston de commutation 85 à la chambre inférieure 101 par un canal 120, et à la chambre supérieure 102 par un canal 121, et d'autre part un canal 119 qui relie le tiroir de commutation 83 au canal 118 d'alimentation.

All these elements constitute the distribution system with control loop, the switching system of which comprises:

• a switching drawer 83 mounted on the pilot lever 50 with a lower chamber 101 and an upper chamber 102 which are located on either side of the switching drawer 83;
• a switching piston 85 mounted in the body 45 and in the extension of the bypass drawer 81, so that the spring 88 of this drawer 81 rests on this piston 85;
• a channel 122 which connects the bottom of the switching piston 85 to the lower chamber 101 by a channel 120, and to the upper chamber 102 by a channel 121, and on the other hand a channel 119 which connects the switching slide 83 to the channel 118 power supply.

The switching piston 85 has at its upper part a recess which constitutes an end chamber 86, into which the channel 122 terminates.

The additional lock 86 of the switching piston 85 is mounted perpendicular to the axis of this switching piston 85, and it is pushed by a spring 89 mounted in a housing of the body 45, so that the additional lock 86 can come engage in a groove 95 which is arranged in the switching piston 85.

The damper is constituted by a damping drawer 84 which is mounted on the pilot lever 50, and which is constituted by a collar 103 which separates a lower chamber 105 from an upper chamber 106, which are connected one and the other to supply channel 118 by connecting to channel 119 a channel 125, this channel 125 being connected on the one hand by the channel 126 to the lower chamber 105, and on the other hand by the channel 127 to the upper chamber 106, the flange 103 having at least one throttle 104 which connects the two chambers 105 and 106.

The elastic return system of the pilot lever 50, which is arranged at the end opposite to the input lever 49, consists of a compression spring 87. This spring 87 is mounted in a housing of the body 45 of the servo valve 41 and it rests on the one hand on the bottom of this housing, and on the other hand against the end of the pilot lever 50.

The switching circuit further comprises a connecting channel 123 which is arranged between the channel 115 returning to the reservoir of the chamber 93 of the bypass drawer 81, and the channel 122 supplying the switching jack 85. This channel link 123 is provided with a throttle 124.

• un tiroir de pilotage 142 qui est monté sur le levier de pilotage 50, et qui est entouré d'une chambre annulaire 157, avec une chambre inférieure 158 et une chambre supérieure 159 qui sont situées de part et d'autre du tiroir de pilotage 142 ;
• un tiroir de by-pass 141 avec une tige 150 sur laquelle est monté un ressort 148, qui s'appuie d'une part sur ce tiroir 141, et d'autre part sur le corps 46, et qui est disposé dans une chambre 153, l'autre extrémité 167 du tiroir de by-pass 141 ayant un chanfrein 152 qui vient en contact contre le fond du corps 46 sous l'action du ressort 148, une chambre annulaire 154 étant disposée autour de ce tiroir 141 qui possède un canal 151 débouchant dans la chambre 153 ;
• la boucle d'asservissement qui a :
  • . un canal 171 qui relie la chambre supérieure 60 du vérin 9 à la chambre annulaire 154 du tiroir de by-pass 141, qui est reliée elle-même par un canal 173 à la chambre annulaire de pilotage 157 ;
  • . et un canal 172 qui relie la chambre inférieure 61 du vérin de puissance 9 au tiroir de by-pass 141, qui est relié lui-même par un canal 174 à la chambre inférieure 158 du pilotage ;
• un canal 178 qui est relié d'une part à l'alimentation du circuit hydraulique, et d'autre part au canal 177 qui aboutit au tiroir de by-pass 141 ; un canal 176 qui est relié au retour au réservoir et qui aboutit dans la chambre 159 de pilotage qui est reliée par un canal 175 à la chambre 153 du tiroir de by-pass 141.

The servo loop distribution assembly of the passive servo valve 42 in normal operation comprises:

• a pilot drawer 142 which is mounted on the pilot lever 50, and which is surrounded by an annular chamber 157, with a lower chamber 158 and an upper chamber 159 which are located on either side of the pilot drawer 142 ;
• a bypass drawer 141 with a rod 150 on which is mounted a spring 148, which rests on the one hand on this drawer 141, and on the other hand on the body 46, and which is arranged in a chamber 153 , the other end 167 of the bypass drawer 141 having a chamfer 152 which comes into contact against the bottom of the body 46 under the action of the spring 148, an annular chamber 154 being arranged around this drawer 141 which has a channel 151 opening into chamber 153;
• the control loop which has:
  • . a channel 171 which connects the upper chamber 60 from the jack 9 to the annular chamber 154 of the bypass drawer 141, which is itself connected by a channel 173 to the annular pilot chamber 157;
  • . and a channel 172 which connects the lower chamber 61 of the power cylinder 9 to the bypass valve 141, which is itself connected by a channel 174 to the lower chamber 158 of the piloting;
• a channel 178 which is connected on the one hand to the supply to the hydraulic circuit, and on the other hand to channel 177 which leads to the by-pass drawer 141; a channel 176 which is connected to the return to the tank and which terminates in the piloting chamber 159 which is connected by a channel 175 to the chamber 153 of the by-pass drawer 141.

• un tiroir de commutation 143 qui est monté sur le levier de pilotage 50 avec une chambre centrale 161 et deux portées : une portée inférieure 160 et une portée supérieure 162 qui sont situées de part et d'autre de cette chambre centrale 161 ;
• un piston de commutation 145 qui est monté dans le corps 46 et dans le prolongement du tiroir de by-pass 141 ;
• un canal 182 qui relie le fond du piston de commutation 145 par des canaux 180 et 181 à la chambre centrale 161 du tiroir de commutation 143, qui est lui-même relié par un canal 179 au canal d'alimentation 178 sous pression ; cette pression agissant sur le piston de commutation 145 pour le maintenir en position basse initiale, un canal 184 étant raccordé au canal 176 relié au retour au réservoir et aboutissant à la portée inférieure 160, et un canal 188 raccordé au canal 184 et aboutissant à la portée supérieure 162.

The circuit for switching the servo loop of the passive servo valve 42 in normal operation comprises:

• a switching slide 143 which is mounted on the pilot lever 50 with a central chamber 161 and two ranges: a lower range 160 and an upper range 162 which are located on either side of this central chamber 161;
• a switching piston 145 which is mounted in the body 46 and in the extension of the bypass slide 141;
• a channel 182 which connects the bottom of the switching piston 145 by channels 180 and 181 to the central chamber 161 of the switching slide 143, which is itself connected by a channel 179 to the supply channel 178 under pressure; this pressure acting on the switching piston 145 to maintain it in the initial low position, a channel 184 being connected to the channel 176 connected to the return to the reservoir and leading to the lower range 160, and a channel 188 connected to the channel 184 and leading to the upper reach 162.

The switching piston 145 has a recess constituting an end chamber 146, which is arranged at its end so that the channel 182 ends in this end chamber 156.

The additional latch 146 of the switching piston 145 is mounted perpendicular to the axis of this switching piston 145, and it is pushed by a spring 149 housed in the body 46, so as to be able to come and engage in a groove 55 which is fitted in this switching piston 145.

The damper mounted on the pilot lever 50 is constituted by a damping drawer 144, and it comprises a collar 163 which separates a lower chamber 165 from an upper chamber 166. These lower chambers 165 and upper 166 are connected to the one and the other to the supply channel 178 by the connection to channel 179 of a channel 185. This channel 185 is itself connected by channel 186 to the lower chamber 165, and by channel 187 to the chamber upper 166. In addition, the collar 163 has at least one constriction 164 which connects the two chambers 165 and 166.

The elastic return system which is mounted on the pilot lever 50, is located at the end opposite to the input lever 49. This elastic return system consists of a compression spring 147, which is mounted on a rod 194 of the pilot lever 50. This compression spring 147 is disposed between two washers, referenced 193, which are arranged one and the other at each of these ends and which are held by a flange 195 arranged at the upper end of the pilot lever 50. One of the washers 193 is applied to a support 189 of the body 46 of the servo valve 42, and the other washer 193 is applied to a support 190 of the body 46.

FIG. 3 represents one of the three servos active in normal positioning, in the case where the entire hydraulic circuit of the power cylinder 9, of the anchoring cylinder 10, and of the servo valve 41 is without pressure, which corresponds to when the helicopter is on the ground. The spring 88 of the bypass drawer 81 pushes this bypass drawer 81 against the bottom of the body 45, and therefore, the bypass drawer 81 engages the latch 51 in the housing 55 of the input lever 49 which is thus locked. The switching piston 85 is pushed against the bottom of its housing of the body 45 by the spring 88 of the bypass drawer. The switching piston 85 is in the unlocked position, and it pushes the additional lock 86 into its housing by compressing the spring 89. The pilot lever 50 is blocked by the lever 49 in its central position, which causes the pilot drawer 82 and the switching slide 83 are also in the central position since they belong to this control lever 50.

The circuit of the servo actuator loop 9 is in by-pass via channel 91 of the by-pass slide 81, that is to say that the upper chamber 60 and the lower chamber 61 of the power cylinder 9 are connected to the reservoir by the channels 115 and 116. The power cylinder 9 is therefore free to be moved according to the position of the controls, in order to follow the non-rotating plate 5.

The lower chamber 61 of the power cylinder 9 being connected to the tank, the anchoring cylinder 10 is hydraulically disengaged. However, this anchoring cylinder 10 is held in the anchoring position by its spring 66, which presses the two pistons 65 respectively against the support 69 and against the edge 70 of the body 63.

FIG. 5 represents one of the three servos active in normal positioning, in the case where the entire hydraulic circuit of the power cylinder 9, of the anchoring cylinder 10, and of the servo valve 41 is put under pressure, which corresponds in the case of the helicopter in normal operation. The pressure of the hydraulic circuit then arrives in the channel 118 and acts on the chamfer 92 and its corresponding face 107 of the bypass drawer 81. The bypass drawer 81 then moves by pushing the spring 88, so as to abut against the switching piston 85. The bypass drawer 81 by moving releases the lock 51 of the housing 55 and the lever input 49 is then unlocked and it can freely control the control lever 50, that is to say the control drawer 82 and the switching drawer 83 which belong to this control lever 50.

The bypass cylinder 81 by moving eliminates the bypass, that is to say the communiction of the channel 91 with the channel 111 of the upper chamber 60, and with the channel 112 of the lower chamber 61 of the cylinder power 9. The bypass cylinder 81 while moving put in communication the supply channel 118 with the channel 112 of the lower chamber 61 of the power cylinder 9, as well as with the channel 114 which leads to the lower chamber 98 of the pilot valve 82. As a result, the circuit of the control loop is supplied, and the chamber 72 of the anchoring cylinder 10 is constantly under pressure, since it is connected via the channel 76 from the chamber 61 and from the channel 112 to the supply channel 118. The anchoring cylinder 10 is thus in the locked position.

The input lever 49 can be moved normally within the usual control range, since it is in the unlocked position. However, the input lever 49 can reach one of these upper 56 or lower 57 stops only after displacement of the end-of-travel damper, that is to say of the damper drawer 84, which is not not possible under normal riding conditions. In addition, the input lever 49 could not be placed in abutment at the time of pressurization, because it was kept neutral by the latch 51 which was engaged in the housing 55.

The hydraulic circuit of the control loop is then under pressure, because the bypass slide 81 has moved under the action of the pressure of the channel 117, to put the lower chamber 61 of the power cylinder 9 into communication with the lower chamber 98 of the control, by means of the channels 112 and 114 which are then connected to the channels 118 and 117 under pressure. Under the action of a movement of the input lever 49, the pilot lever 50 also moves and drives the pilot valve 82, which moves to put the upper chamber 60 of the power cylinder 9 into communication with the chamber lower 98 or with the upper piloting chamber 99, in the direction of movement of the piloting lever 50, so that the body 47 of the power cylinder 9 moves until the return to the equilibrium position of the pilot valve 82.

Figure 6 shows one of the three servos active in normal positioning, in the event of a failure, caused for example by a projectile impact which causes the blocking of the power cylinder 9. The servo can then no longer move , and the piloting effort brings the input lever 49 to one of these upper 56 or lower 57 stops, by moving the drawer 84 of the damper.

The pilot lever 50 therefore moves up or down by a value greater than the accepted value, and it puts the switching circuit into communication with the supply channel 118. In fact, the pilot lever 50 by moving causes the switching slide 83 downward or upward, which allows the channel 122 terminating in the cavity 96 of the switching piston 85 to be in communication with the channel 119 which is connected to the supply channel 118. For this, the piloting lever 50 while moving put in communication the lower chamber 101 or the upper chamber 102 of the communication drawer 83 with on the one hand the channel 119, and with on the other hand either the channel 120 , i.e. the channel 121 which are both connected to the channel 122 leading to the switching piston 96. In the case shown in FIG. 6, there has been a downward displacement of the pilot lever 50, and it is the upper chamber 102 which puts the piston 85 in communication with the supply channel 118 by l intermediate of the channels 122, 121 of the upper chamber 102, and of the channel 119. The pressure then acts in the cavity 96 of the switching piston 85 which moves downwards, that is to say in the direction of the arrow shown in Figure, which then pushes the bypass drawer 81 until its face 107 abuts against the bottom of the housing of the body 45.

Figure 7 is a Figure similar to Figure 6, that is to say which represents one of the three active servos in the normal position, in the case where this servo was deactivated immediately after the failure. The switching piston 85, as seen for Figure 6, therefore moved to get into the emergency position, that is to say the position which corresponds to that where the bypass drawer abuts by its face 107 against the bottom of the housing of the body 45. The bypass drawer 81 then puts the upper chamber 60 and the lower chamber 61 of the power cylinder 9 into communication with the return to the tank. For this, the channel 91 of the bypass drawer 81 puts in communication the channel 112 connected to the lower chamber 61, and the channel 114 connected to the lower chamber 98 of the control drawer 82 with the chamber 93, which is itself even connected to the reservoir via the channel 115, the chamber 99 of the pilot valve 82, and the channel 116. The bypass valve 81 in this position also connects the channel 111 connected to the upper chamber 60 of the power actuator, and the channel 113 connected to the annular chamber of the pilot valve 82 in communication with the chamber 93 by the annular chamber 94.

The circuit of the servo actuator loop is thus connected to the tank, that is to say that the upper chamber 60 and the lower chamber 61 are connected to this tank and that therefore, the chamber 72 of the anchoring cylinder is also connected to the return to the tank.

The switching piston is in the emergency position, and its position is maintained by means of the additional lock 86 which engages in the groove 95 of the switching piston 85. On the other hand, the bypass drawer 81, moving down, engaged the latch 51 in the housing 55, which blocks the input latch 49 in the locked position, and returns the pilot lever 50 to the central position. The servo control then becomes inoperative and it is held in this position, where it is neutralized by the switching jack 85. As a result, this servo control can follow the movements of the non-rotating plate 5 without having any action on it, due to that all of the chambers of the power cylinder 9 and of the anchoring cylinder 10 are placed on the return to the tank.

Figure 4 shows the passive servo control in normal position, in the case where the entire hydraulic circuit of the power cylinder 9, the anchoring cylinder 10, and the servo valve 43 is without pressure, which corresponds to the case of the helicopter on the ground. The spring 148 of the bypass drawer 141 pushes this bypass drawer 141 until its face 167 abuts against the bottom of the housing of the body 46. The bypass drawer 141 then pushes the latch 51 into the housing 55 of the input lever 49, which is then locked in its central position. As a result, the pilot lever 50 is also locked in the central position, and it is the same for the pilot drawer 142, for the switching drawer 143, as well as for the damper drawer 144. The upper chamber 60 and the lower chamber 61 of the power cylinder 9 are connected to the return to the tank by the channel 151 of the by-pass drawer 141, which ends in the chamber 153 connected to the channels 175 and 176 of the return to the tank. The cylinder power is therefore by-pass and it is free to be moved according to the position of the controls.

The chamber 72 of the anchoring cylinder 10 is connected to the lower chamber 61 of the power cylinder 9 by the channel 76, and therefore, this chamber 72 is also connected to the return to the tank. The anchoring cylinder 10 is thus disengaged hydraulically, but it is held in the anchoring position by the spring 66. In fact, this spring 66 pushes the two pistons 65 respectively against the bearing face 69 and against the edge 70 of the body 63.

The servo drive is passive, the input lever 49 is locked, and the power cylinder 9 being in by-pass can be moved according to the position of the controls.

Figure 8 shows the passive servo in normal position, in the case where the circuit is pressurized, which corresponds to the case where the helicopter is in operation. The pressure arrives via the channel 178, and it is established in the channel 177. Therefore, the pressure pushes the bypass valve 141 against the switching piston 156. The supply channel 178 also puts in pressure the channel 179 which supplies the damper drawer 144, and the switching circuit. The upper 166 and lower 165 chambers of the switching drawer 144 are thus supplied via the channels 187 and 186 respectively which are connected to the channel 179 via the central channel 185. The switching circuit is supplied by the central chamber of the switching slide 143, which is connected on the one hand to the channel 179, and on the other hand to the channel 182 which terminates in the cavity 156 of the switching piston 155, via the two parallel channels 180 and 181 which terminate both in this central chamber 161 of the switching slide 143. The switching piston 156 thus abuts against the bottom of its housing, and this switching piston 145 can thus serve as a stop for the by-slide pass 141 which remains in this position by the effect of the pressure prevailing in the channel 177, and which acts on the face 167 and the chamfer 152. The by-pass drawer 141 while moving has released the lock 51 of the housing 55, and therefore, the input lever 49 is unlocked, while leaving the upper 60 and lower 61 chambers of the jack 9 connected to the return to the tank, so that the passive servo valve 42 remains inoperative.

The passive servo control does not work and is driven in these movements by the swashplate. The transient or permanent position deviation with the control linkage is absorbed by the input clearance, that is to say by the possible displacement of the input lever 49. In fact, this displacement must be sufficient for the upper 56 and lower 57 stops are not reached.

The anchoring cylinder 10 is disengaged, but the spring 66 maintains it in the middle position, to impose that the displacement of the passive servo-control be made by the sliding of the power cylinder 9, as if it were slaved. This makes it possible to avoid the drift towards an abutment of the anchoring cylinder 10 and of the piston 58 of the servo-control.

Figure 9 represents the passive servo control in normal position with its hydraulic circuit under pressure, at the moment when a breakdown caused by a fire occurred on one of the three active servo controls in normal position. As has been seen with respect to FIG. 7, this servo-control is then neutralized, and the circuit goes to the position shown in this Figure. The non-rotating plate 5 is then no longer maintained except by two active servos, and it therefore exerts a force on the passive servo. The input lever 49 of this passive servo drive is maintained by the wheelhouse, and it is brought into abutment against one of the upper 56 or lower 57 stops. The input lever 49 while moving drives the pilot lever 50, which moves up or down by a value greater than the accepted value. In this movement, the control lever 50 also drives the control drawer 142, the drawer 144 of the damper, and the switching drawer 143. This movement causes the switching circuit to be placed in the reservoir, because the central chamber 161 of the switching drawer 143 is then in communication with the return channel to the tank 176, via the channel 188 which is connected to this central chamber 161 via the channel 184. The central chamber 161 of the drawer switching 143 is in fact connected by one of the channels 180 and 181 to the cavity 156 of the switching piston 145 via the channel 182. In the case of FIG. 9, the displacement of the pilot lever 50 has downward, and it is channel 180 which is in communication with channels 184 and 176. The pilot lever 50 while moving has also closed the communication between the switching circuit and the supply channel 178, by the channel 179 which is blocked by the bearing of the pilot lever 50. The switching circuit then being in communication with the tank, the bypass slide 141 can then move under the action of the pressure of channel 177 which acts on the face 167 of this bypass drawer 141, which can thus push the switching piston 145 in the direction of the arrow, so that the bypass drawer 141 can close.

Figure 10 is a Figure similar to Figure 9 which shows the passive servo in normal position, and in which the bypass slide 141 has completed its stroke which caused it to push the switching piston 145 into abutment against the bottom of its housing in the casing 46. As a result, the by-pass slide 141 while moving thus put the supply channel 178 into communication with the circuit of the servo piston piston 9, that is to say that it has put the supply channel 178 into communication with the channels 151 and 174 via the channel 177. The channel 151 being connected to the lower chamber 61 of the power cylinder 9, and the channel 174 being connected to the lower chamber 158 of the control drawer 142. The by-pass drawer 141 while moving has also closed the communication with the reservoir of channels 173 and 171 of the loop circuit d servo in correspondence with the upper chamber 60 of the power cylinder 9.

The supply pressure 178 via the channel 177 also feeds, via the channel 151 and the lower chamber 61 of the power cylinder, the chamber 72 of the anchoring cylinder 10 via the channel 76 .

As can be seen in the Figure, the switching piston 145, by moving to abut upwards in the bottom of its housing in the body 46, has enabled the additional lock 146 to come and engage in the groove 155 of the switching piston 145 under the action of its spring 149, in order to block this switching piston 145 so that this switching piston 145 remains in the backup position.

Thus, during a failure on one of the three active servos in normal operation, the pilot lever 50 of the passive servo moves up or down, by a value greater than the accepted value, and it connects the central piloting chamber 161 with one of the channels 184 and 188 which are connected to the return to the tank. The switching piston 145 can then move under the action of the bypass drawer 141, which is pushed by pressure to go into the emergency position. The bypass drawer 141 therefore places the lower chamber 61 of the power cylinder 9 in communication with the lower chamber 158 of the control drawer 142 by channels 172 and 174, which are thus connected to channel 178. In addition, the bypass drawer 141 eliminates the connection with the return to the reservoir of the upper chamber 60, and the normally passive servo control becomes operational.

The servo control is then active and maintained in this position by the fact that the switching piston is locked by the additional latch 146, which guarantees the closing of the bypass and which allows the supply of the circuit of the control loop. of the power cylinder 9, and the supply of the anchor cylinder 10.

The reduced vulnerability device according to the invention thus makes it possible to maintain normal piloting in the event of a failure caused by a projectile impact on one of the active servos, and this without the intervention of the pilot. In addition, the device of the invention also makes it possible to guarantee the normal operation of the piloting in the case of other possible causes, as indicated below.

The blocking of the cylinder 9 of the passive servo-control does not disturb the normal operation of the piloting, owing to the fact that the anchoring cylinder 10 is disengaged.

The blocking of an anchoring cylinder 10 without hydraulic leakage from any of the three commands active in normal operation does not cause disturbance in the operation of the entire device.

In the event of a hydraulic leak for any reason on one of the three normally active servos, this servo is then neutralized, and the normally passive servo moves to the save position, as described above. In the event of a hydraulic leak for any reason on the passive servo control, there is no consequence on the piloting and the loss of pressure is simply reported to the pilot.

In the event of a break in the input lever 49, or in the linkage 13 for controlling one of the servo-controls active, the spring 87 placed at the end of the control lever 50 pushes the latter and the switching takes place so that this servo-control is neutralized and the passive servo-control moves to the save position, as indicated above . In the event of a break in the input lever 49 or the linkage 13 for controlling the passive servo control, the pilot lever 50 remains in the middle position due to the action of the latch 51 pushed by the spring 148, and the servo drive remains disengaged.

In the event of the rupture of one of the three normally active servos or its corresponding anchoring, the servo then becomes inoperative, and the passive servo goes into the save position, as indicated above. In the event of a break in the passive servo drive or its anchoring, there is no consequence on the steering.

Claims (39)

1. Low-vulnerability device for the operation of a lifting and propulsing rotor of a helicopter by means of a cyclic plate mechanism mounted coaxially on the rotor drive shaft (6), in which the rotating plate is coupled by its peripheral part individually to a rod for controlling the pitch of each rotor blade, and in which the non-rotating plate (5) is coupled at four points (1, 2, 3, 4) regularly distributed around its periphery to four hydraulic actuating servocontrols each comprising a power jack (9), an anchoring system (10) and a servocontrol-distributor (41, 42), three of the servocontrols being used in normal working and the fourth being used as back-up in the event of a failure occurring on one of the other three,
   characterized in that:

   - each power jack (9) is supplied by a hydraulic circuit, independent of the hydraulic circuits of the other jacks (9), and comprises the servocontrol-distributor (41,42) operated by a mechanical input which is linked to the cockpit by a control linkage (13);

   - each power jack (9) comprises a disengageable anchoring system;

   - three of the servocontrol-distributors (41) are structurally arranged so as to be active in normal working and to block the anchoring system of each corresponding jack (9), and one servocontrol-distributor (42) is structurally arranged so as to be passive in normal working and to keep the anchoring system of the corresponding power jack (9) disengaged;

   - each mechanical input of these four servocontrol-distributors (41,42) comprises a system which in the event of a certain force threshold being exceeded on one of the three normally active servocontrol-distributors (41), neutralizes this servocontrol-distributor and initiates the starting up of the normally inactive servocontrol-distributor (42) which then becomes operational in the safeguard working mode.
2. Device according to claim 1, characterized in that each servocontrol-distributor (41, 42) is incorporated in the corresponding power jack (9) so as to form a monoblock assemby (43,44) consisting of the body (45,46) of the servocontrol-distributor (41,42) and the body (47) of the power jack (9).
3. Device according to one of the preceding claims 1 or 2, characterized in that each servocontrol-distributor (41,42) comprises:

   - a distribution assembly with a control loop between the position of the body (47) of the power jack (9) and the position of the corresponding mechanical input;

   - a system for switching this control loop so as to place it in the opposite state to that corresponding to normal working of the control system of the non-rotating plate (5).
4. Device according to claim 3, characterized in that the control loop receives feedback information concerning the position of the body of the power jack (9), which acts directly on the position of the mechanical input mounted on the monoblock assembly (43,44) by means of a control system linked to the mechanical input, in such a way so that any change in the position of the mechanical input in relation to the monoblock assembly (43,44) in response to a pilot manoeuver causes displacement of the body (47) of the power piston (9), i.e. the displacement of monoblock assembly (43,44), until the mechanical input returns to its initial relative position in relation to this monoblock assembly (43,44).
5. Device according to claim 4, characterized in that the control loop is linked to the supply pressure of the corresponding independent hydraulic circuit, and in that the control system is connected to the fluid reservoir of this independent circuit.
6. Device according to one of claims 4 and 5, characterized in that the control system comprises an actuator valve (82,142) linked to the mechanical input.
7. Device according to any one of claims 3 to 6, characterized in that the power jack (9) has a differential section, and comprises a piston (58) with a rod (59) linked to the anchoring system, in such a way as to provide an upper chamber (60) and a lower chamber (61) on the side of the rod (59) and which are connected to the control loop, in such a way that when the power jack (9) operates, the lower chamber (61) is always connected to the pressurized hydraulic circuit.
8. Device according to claim 7, characterized in that the control loop switching system comprises:

   - a by-pass valve (81,141) of the power jack (9) which is mounted in the control loop;

   - a two position switching piston (85, 145);

   - a switching distributor which acts on the switching piston (85, 145) to provide two positions:

   . an initial position in which the switching piston (85,145) works with the by-pass valve (81,141) to obtain normal working of the servocontrol-distributor (41, 42) of the corresponding power jack (9);

   . a back-up position in which the switching piston (85,145) works with the by-pass valve (81,141) to obtain safeguard working of the servocontrol-distributor (41,42) of the corresponding power jack (9).
9. Device according to claim 8, characterized in that the by-pass valve (81,141) is mounted on the supply channel (117,118; 177,178) of the control loop, and is connected to the fluid reservoir in such a way that this by-pass valve (81,141) has at least two positions:

   - one position corresponding to the control loop without pressure,

   - one working position of the servocontrol-distributor (41,42) corresponding to the control loop under pressure.
10. Device according to one of claims 8 and 9, characterized in that the switching piston (85,145) is locked in the back-up position by an additional lock (86,146).
11. Device according to any one of the preceding claims, characterized in that the mechanical input has a lock (51).
12. Device according to claims 8 and 11, characterized in that the by-pass valve (81,141) carries the lock (51) which acts on the mechanical input.
13. Device according to any one of claims 8 to 12, characterized in that the actuator valve (82, 142) and the switching distributor (83, 160) belong to the same part, i.e. the actuator lever (50) linked to the mechanical input made up of an input lever (49).
14. Device according to claim 13, characterized in that the actuator lever (50) comprises an elastic return system at the end facing the input lever (49).
15. Device according to claim 14, characterized in that the elastic return system comprises a compression spring (87) mounted between the body (45) of the servocontrol-distributor (41) and the end of the actuator lever (50).
16. Device according to claim 14, characterized in that the elastic return system comprises a compression spring (147) mounted on a rod (194) of the actuator lever (50) between two washers (193) arranged at each of its ends and held in position by a collar (195), one washer (193) pressing against a bearing face (189) on the body (46) of the servocontrol-distributor (42), and one washer (193) pressing against a bearing face (190) of this body (46).
17. Device according to any one of claims 13 and 14, characterized in that the mechanical input is formed by the input lever (49) which is mounted under the body (45,46) of the servocontrol-distributor (41,42) by means of an articulation (52) located at one of its ends, the other end receiving the input movement via the corresponding system, the actuator lever (50) being linked to the input lever (49) by an articulation (53) located between the movement input and the mounting articulation (52) of this input lever (49).
18. Device according to claim 17, characterized in that the input lever (49) works with two end stops: one upper end stop (56) and one lower end stop (57) which are integral with the body (45,46) of the servocontrol-distributor (41,42).
19. Device according to any one of claims 17 and 18, characterized in that the input lever (49) comprises a recessed hole (55) made in the upper side of the mounting articulation (52), this recessed hole (55) receiving the lock (51) carried by the by-pass valve which locks the input lever (49).
20. Device according to claim 19, characterized in that this recessed hole (55) and lock (51) have conjugate shapes in the form of a substantially truncated cone.
21. Device according to any one of claims 17 to 20, characterized in that the mounting articulation (52) of the input lever (49) is supported by two lugs (54) made under the body (45,46) of the servocontrol-distributor (41,42).
22. Device according to any one of claims 13 to 21, characterized in that the actuator lever (50) comprises a damper.
23. Device according to claim 21, characterized in that each of the three active servocontrol-distributors (41) when normally working comprises:

    - an actuator valve (82) mounted on the actuator lever (50) and surrounded by an annular chamber (97) with a lower chamber (98) and an upper chamber (99) located each side of the actuator valve (82);

    - a by-pass valve (81) with a rod (90) on which is mounted a spring (88) which presses on the one hand against this valve (81), and on the other hand against the body (45) and which is arranged in a chamber (93), the other end (107) of the by-pass valve (81) having a bevelled edge (92) which, under the action of the spring (88), comes into contact with the body (45), an annular chamber (94) being arranged around this valve and which has a channel (91) leading into the chamber (93);

    - the control loop having a channel (111) which connects the upper chamber (60) of the power jack (9) to the annular chamber (94), which is itself connected by a channel (113) to the annular chamber (97) of the actuator valve, and a channel (112) connecting the lower chamber (61) of the power jack (9) to the by-pass valve (81) which is connected by a channel (114) to the lower chamber (98) of the actuator valve;

    - a channel (118) connected to the supply of the hydraulic circuit and to the channel (117) which leads to the by-pass valve (81);

    - a channel (116) connected to the return to the fluid reservoir leading to the upper chamber (99) of the actuator valve, said chamber being linked by a channel (115) to the chamber (93) of the by-pass valve (81);

    - in such a way that when the hydraulic circuit is under pressure, the by-pass valve (81) moves as a result of the pressure in channel (117) to connect the lower chamber (61) of the power jack (9) to the lower chamber (98) of the actuator valve via the channels (112,114), which are thus connected to the pressurized channels (118) and (117) and in that in response to movement of the actuator lever (50), the actuator valve (82) moves so as to connect the upper chamber (60) of the jack (9) to either the lower chamber (98) or to the upper chamber (99) of the actuator (50) depending on the direction of movement of the lever, causing the body (47) of the jack to move until the actuator valve (82) returns to the balancing position.
24. Device according to claim 23, characterized in that each of the three active servocontrol-distributors (41) when normally working comprises:

    - a switching valve (83) mounted on the actuator lever (50) with a lower chamber (101) and an upper chamber (102) located each side of the switching valve (83);

    - a switching piston (85) mounted in the body (45) and in the continuation of the by-pass valve (81), in such a way that the spring (88) of this valve (81) bears against this piston (85);

    - a channel (122) connecting the bottom of the switching piston (85) to the lower chamber (101) via channel (120), and to the upper chamber (102) via channel (121), a channel (119) connecting the switching valve (83) to the supply channel (118);

    - in such a way that when the actuator lever (50) moves upwards or downwards by a value greater than the permitted value, it connects one of the chambers (101) and (102) to the channel (119) under pressure, the pressure then being sent via channel (122) to act on the switching piston (85) which moves to the back-up position and pushes back the by-pass valve (81) which then connects the chambers (60) and (61) of the power jack (9) to the return to the fluid reservoir (115,116), via the channels (112) and (114) which lead into channel (91) connected to the chamber (93), and via the channels (111) and (113) in which the annular chamber (94) is thus connected to the chamber (93).
25. Device according to claim 24, characterized in that the end of the switching piston (85) comprises a bevelled shoulder forming an end chamber (96).
26. Device according to any one of claims 24 and 25, characterized in that the additional lock (86) is mounted perpendicular to the axis of the switching piston (85), this additional lock (86) being pushed by a spring (89) in such a way as to engage in a groove (94) made in the switching piston (85).
27. Device according to claim 22 and any one of claims 23 to 26, characterized in that each of the three active servocontrol-distributors (41) when normally working comprises a damper valve (84) mounted on the actuator lever (50) with a collar (103) separating a lower chamber (105) from an upper chamber (106), both of these chambers being connected to the supply channel (118) via the branch on channel (119) of a channel (125) connected via channel (126) to the lower chamber (105) and via channel (127) to the upper chamber (106), the collar (103) having at least one throttling (104) linking the two chambers (105) and (106).
28. Device according to any one of claims 24 to 27, characterized in that each of the three active servocontrol-distributors (41) comprises a link channel (123) between the fluid reservoir return channel (115) and the supply channel (122) of the switching piston (85), this link channel (123) comprising a throttling (124).
29. Device according to claim 21, characterized in that the passive servocontrol-distributor (42) when normally working comprises:

    - an actuator valve (142) mounted on the actuator lever (50) and surrounded by an annular chamber (157), with a lower chamber (158) and an upper chamber (159) located each side of the actuator valve (142);

    - a by-pass valve (141) with a rod (150) on which a spring (148) is mounted which presses on the one hand against this valve (141) and on the other hand against the body (46), and which is arranged in a chamber (153), the other end (167) of the by-pass valve (141) having a bevelled edge (152) which, under the action of the spring (148), comes into contact with the body (46), an annular chamber (154) being arranged around this valve (141) which has a channel (151) leading into the chamber (153);

    - the control loop having:

    . a channel (171) which connects the upper chamber (60) of the jack (9) to the annular chamber (154) of the by-pass valve (141) which is itself connected via a channel (173) to the annular chamber (157) of the actuator valve;

    . and a channel (172) connecting the lower chamber (61) of the jack (9) to the by-pass valve (141), which is connected via a channel (174) to the lower chamber (158) of the actuator valve;

    - a channel (178) connected to the supply of the hydraulic circuit and to channel (177) which leads to the by-pass valve (141); a channel (176) connected to the fluid reservoir return and leading to the upper actuator chamber (159) which is connected via a channel (175) to the chamber (153) of the by-pass valve (141);

    - in such a way that when the hydraulic circuit is under pressure, the by-pass valve (141) is moved by the pressure in the channel (177) while at the same time leaving the upper chamber (60) and lower chamber (61) of jack (9) connected to the return to the fluid reservoir, so that the passive servocontrol-distributor remains inoperative.
30. Device according to claim 29, characterized in that the passive servocontrol-distributor (42) when normally working comprises:

    - a switching valve (143) mounted on the actuator lever (50) with a central chamber (161) and two lands: one lower land (160) and one upper land (162) located each side of this central chamber (161);

    - a switching piston (145) mounted in the body (46) and in the continuation of the by-pass valve (141);

    - a channel (182) connecting the bottom of the switching piston (145) via two channels (180) and (181) to the central chamber (161) of the switching valve (143) which is connected by a channel (179) to the pressurized supply channel (178), this pressure acting on the switching piston (145), to hold it in the initial lower position, a channel (184) being connected to channel (176) connected to the fluid reservoir return leading to the lower land (160) and a channel (188) connected to channel (184) leading to the upper land (162);

    - in such a way that when the actuator lever (50) moves upwards or downwards by a value that exceeds the permitted value, it connects the central chamber (161) to one of the channels (184) and (188) connected to the fluid reservoir return, the switching piston (145) then being able to move under the action of the by-pass valve (141) pushed by the pressure to assume the back-up position, this by-pass valve (141) thus connecting the lower chamber (61) of the jack (9) and the lower chamber (158) of the actuator valve (142) via the channels (172) and (174) which are thus connected to the supply channel (178), and the by-pass valve (141) removes the link between the fluid reservoir return and the upper chamber (60), and the servocontrol-distributor (42) becomes operational.
31. Device according to claim 30, characterized in that the end of the switching piston (145) comprises a bevelled shoulder forming an end chamber (156).
32. Device according to any one of claims 30 and 31, characterized in that the additional lock (146) is mounted perpendicular to the axis of the switching piston (145), this additional lock (146) being pushed by a spring (149) in such a way as to engage in a groove (155) made in the switching piston (145).
33. Device according to claim 22 and any one of claims 29 to 32, characterized in that the passive servocontrol-distributor (42) when normally working comprises a damper valve (144) mounted on the actuator lever (50) with a collar (163) separating a lower chamber (165) from an upper chamber (166), both of these chambers being connected to the supply channel (178) via the branch on the channel (179) of a channel (185) connected via the channel (186) to the lower chamber (165) and via the channel (187) to the upper chamber (166), the collar (163) having at least one throttling (164) linking the two chambers (165) and (166).
34. Device according to any one of claims 7 to 33, characterized in that the anchoring system comprises an anchoring jack (10) with means of connecting to the power jack (9) and whose hydraulic circuit is connected to the lower chamber (61) of this power jack (9), the anchoring jack (10) being connected to a structural element (11) of the helicopter by anchoring means.
35. Device according to claim 34, characterized in that the anchoring jack (10) comprises a body (63) with a rod (64) carrying two pistons (65) which slide in the body (63) and which, together with the rod (64) and the body (63), determine a chamber (72).
36. Device according to claim 35, characterized in that the rod (59) of the power jack (9) and the rod (64) of the anchoring jack (10) are a single and same part constituting the means of connecting the anchoring jack (10) to the power jack (9).
37. Device according to claim 36, characterized in that the hydraulic supply circuit of the anchoring jack (10) is made up of a channel (76) made in the rods (59) of the power jack (9) and (64) of the anchoring jack (10), in such a way so as to directly link the chamber (72) of the anchoring jack (10) to the lower chamber (61) of the power jack (9).
38. Device according to any one of claims 35 to 37, characterized in that the two pistons (65) are held on the rod (64) by a collar (67) and by an end collar (68), both belonging to this rod (64), a spring (66) pushing back both pistons (65) in relation to one another to hold them in position, one piston (65) pressing against a bearing face (69) of the body (63) and the other piston (65) pressing against the edge (70) of this body (63).
39. Device according to any one of claims 34 to 38, characterized in that the means for coupling comprise an articulation (74) connected on the one hand to a structural element (11) of the helicopter and on the other hand to the bottom (71) of the body (63) of the anchoring jack (10).

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